Description of Application (adapted from the Abstract): Women who use drugs, (i.e. heroin, crack and/or cocaine), through either injected or non-injected routes of administration, are at high risk of acquiring HIV and other blood borne and sexually transmitted infections, such as HBV and HCV. These women are at a higher risk of becoming infected with these pathogens than are non-drug using women and may be at higher risk than male drug users. In order to prevent infection with HIV, as well as with HBV and HCV, among women who use drugs, we need to determine the factors at different causal levels that increase women's risk of acquiring these infections. Biological and behavioral risk factors have already been examined in depth. However, little research currently exists for other causal levels, particularly the influence of structural (i.e., economic and social benefits) and network factors on HIV risk among women who use drugs. Moreover, recent changes in institutional policies concerning the economic and social benefit resources available to women may also contribute to an increase in risk. This exploratory/developmental study proposes to apply the precepts of an evolving theoretical paradigm, "eco-epidemiology," which is predicated on the need to assess and analyze both determinants and outcomes at different levels of organization. The proposed study will employ both ethnographic and epidemiologic techniques to achieve the specific aims that are consistent with this paradigm. The first specific aim of the proposed research is to develop a contextualized understanding of the linkages among structural/institutional factors, and network, relationship and behavioral risk for women who use drugs. This aim will rely on qualitative ethnographic techniques to study 60 women who use drugs (20 participants in two focus groups and 40 participants in in-depth life history interviews). In ethnographic data analyses, two main factors will be examined. Firstly, the extent to which (a) resource dependence increases the likelihood that women who use drugs enter into relationships with or are involved in networks with other drug users will be addressed, as well as whether (b) other drug users in women's networks are high risk, engaging in high risk drug use and sex practices (i.e., the "resource dependence" hypothesis). A second aim of the proposed research is to immediately employ the results from ethnographic data analyses to develop a structured network and social resource questionnaire. This questionnaire will be pilot-tested with a sample of 25 young women who use drugs, and will be assessed for construct validity using data generated from the ethnography. The research is designed to increase understanding of the structural, network and behavioral determinants of HIV risk among women who use drugs. It has the potential to contribute towards finding practical answers to questions on how to develop interventions among women who use drugs; and will provide a basis to generate new hypotheses for a full-scale epidemiologic study using standard survey techniques and network analysis.